1. Field of the Invention:
The present invention relates generally to electronic locating and annunciating systems, and, more particularly, to a continuous locating and annunciating system for maintaining a registry of the locations of classes of personnel and for annunciating their locations.
2. Description of the Prior Art:
The need to maintain an up-to-date registry of personnel in a building or facility is oftentimes required to allow efficient operation of a facility. In some situations, such as a hospital setting, for example, the ability to quickly locate operating personnel can, at times, be of critical importance. As a result, many systems have been developed in order to monitor the location of personnel, or, at least to make annunciations in order to allow personnel to respond to such.
One of the simplest methods of locating personnel within a facility involves merely installing a network of loudspeakers, or the like, spaced throughout the facility. When personnel are to be located, an announcement is broadcast over the loudspeakers. The personnel can then respond to the announcement. Such systems suffer from the inherent disadvantage that the personnel must both hear the broadcast announcement, and make some active response thereto. Additionally, the broadcast announcement distracts all personnel within hearing distance of the loudspeakers, and not just those personnel who are to be located. Furthermore, through such a method, maintaining an up-to-date registry system for monitoring the location of personnel is impractical.
As a result, more elaborate systems have been developed in the prior art for monitoring the locations of personnel in a facility. Ideally, the system is non-intrusive, and does not require the active response of personnel.
Disclosed in U.S. Pat. Nos. 3,439,320; 3,696,384; and 3,739,329 are personnel monitoring systems which utilize portable transceivers carried by the personnel. The transceivers transmit ultrasonic frequency waves. The systems operate using a "scan/respond" format in which the portable transceivers transmit signals responsive to reception of a "scan" signal generated by a remote transmitter. Because the transceiver is operative only when the transceiver is "scanned", power consumption of the transceiver is minimized. Several problems are inherent, however, in ultrasonic scan/respond systems. First, if the personnel carrying the transceiver travels beyond the range of the scan signal, the transceiver does not transmit a signal in response, and an erroneous registry indication results. In order to minimize this problem, the systems are designed in order to function at maximum transmission ranges. To allow functioning in this range, the transceivers must be designed to operate at high energy levels, resulting in excessive battery drain.
Operation of the systems at high transmission energies results in additional problems. When an ultrasonic signal is transmitted at a high energy level, the ultrasonic frequency signal may be transmitted through a boundary, such as a wall, resulting, again, in erroneous indications of the location of personnel. In fact, when transmitting at the high energy levels, the registry systems may indicate that one person is in several locations at the same time.
Prior art systems have been developed utilizing infrared frequency transmitter/receivers. For example, disclosed in German patent number 3210002 is a system in which infrared light emitters transmit periodic signals whose detection by an infrared receiver energizes relays to register the presence of a person carrying the infrared emitters. No means, however, is disclosed for preventing signal overlap between two different periodic signals transmitted by emitters carried by two different individuals. Additionally, the infrared emitters transmit the periodic signals constantly, which degradates battery longevity.
Also, disclosed in U.S. Pat. No. 4,275,385 is a personnel locating system which maintains a registry of individuals by tracking their entry and exit from defined areas. Each person carries a portable transmitter, and each transmitter transmits a unique sixteen bit binary codeword with start, stop and parity bits employing infrared light emitting diodes. Infrared receivers are positioned to allow detection of the binary codeword transmitted by the transmitter. However, the receiver can only detect the transmitted codeword over a limited range, and only when the receiver is positioned so as to be in the "line of sight" of the transmitter. To overcome this problem, the receivers are positioned in doorways to rooms forming the defined area. When a person carrying a transmitter passes through the doorway, such passage is detected. The system therefore actually tracks the entrance and exit of personnel from the rooms rather than continuously maintaining the locations of the personnel. As a result, this prior art system also suffers from several inherent disadvantages. First, because a receiver only detects the transmitted signal during the brief period of time in which personnel pass through a doorway, any transmission problem occurring during this period of time results in the entry and/or exit of the personnel not to be registered. Because a unique multi-bit codeword, as well as parity and stop/start bits must be transmitted in sequence by a portable transmitter in order to correctly identify the personnel passing through the doorway, any bit error results in an incorrect registry entry. Additionally, the number of receivers required to maintain an accurate registry of personnel increases greatly if a room contains more than one doorway allowing entrance and exit. A still further disadvantage inherent to this system occurs when two or more individuals enter through a doorway simultaneously either in close proximity to one another (i.e., within the envelope of the receiver). The receiver cannot differentiate between the transmitted signals as the start bits transmitted by each transmitter prevents the receiver from detecting the presence of any transmitter. Again, an erroneous registry indication results as no individual is registered as entering and/or exiting through the doorway. Still further, an erroneous registry indication also results when personnel pass within the envelope of the receiver, but do not pass through the doorway. For example, in a hospital setting, personnel walking along a hallway may pass within the envelope of several receivers positioned in the doorways of several rooms, but enter none of the rooms. The system would register such personnel in all of the rooms at the same time. In a hospital setting, such false information is actually more detrimental than no information at all.
As mentioned hereinabove, a locating system allowing quick location of operating personnel is oftentimes of critical importance in a hospital setting. Broadcasting announcements over loudspeakers is, of course, impractical in a hospital setting, and other prior art systems for creating and maintaining an up-to-date registry system of hospital personnel suffer from disadvantages, as mentioned hereinabove.
In a hospital setting, an up-to-date registry is also needed in order to create and maintain a historical record of the locations of members of classes of personnel. Accurate records of the locations of classes of personnel must also be maintained for future reference, such as, for example, in the event of subsequent litigation. No prior art registry system is known which tracks the locations of classes of personnel directly. Prior art systems, such as the one disclosed in U.S. Pat. No. 4,275,385 track the locations of individuals. And as mentioned hereinabove, several inherent disadvantages are associated with this system, thereby limiting its usefulness.
It is, accordingly, an object of the present invention to provide a personnel locator system for locating personnel in a facility.
It is a further object of the present invention to provide a personnel locating system which detects the presence and the continued presence of personnel.
It is a yet further object of the present invention to provide an infrared personnel locator system which overcomes the disadvantages associated with prior art infrared systems.
It is a still further object of the present invention to provide a personnel locating and monitoring system for maintaining a registry of locations of classes of personnel in a hospital setting.